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Stockton Meat Plant - Case Closure Page 10 March, 1996 Figure 3, groundwater elevation changed little from August 1992 to f November 1994 Elevations in March 1995 rose sharply, apparently in direct response to the high rainfall totals that occurred in the winter of 1995 Using the above Krazen report reference to MW-5 depth to ground water of 24 5 feet below ground surface in September, 1995, the ground water elevation in MW- ' 5 was approximately 18 4 feet below mean sea level This matches closely the elevation in March, 1995, thus, indicating groundwater in the area may be stabilizing at a higher relative elevation for 1995. ' Figure 4 is a comparison, b monitoring well, of changes in diesel � P Y g concentration with time The April 1994 sample was reported with a high detection limit and all samples were reported less than 1 mg/l Thus, the dashed lines between earlier and later sampling events Correlation between groundwater elevation (Figure 3) and diesel concentration is difficult to determine In general there appears to be a ground water elevation correlation with MW-5 and MW-6 As groundwater elevation increases 6 e rises toward the surface) or decreases, there is a corresponding increase and ' decrease in the diesel concentration MW-4 does not track as well There is a counter-trend in November 1994, when with lower groundwater elevation, the diesel concentration in MW-4 increases relative to the July, 1994 sampling event However, the differences are small and can be attributable to sampling, degradation during transit to laboratory, analytical extraction errors, and instrument sensitivity, especially when the analytical results are reported in parts per billion range BENEFICIAL USES OF GROUNDWATER Most of the ground water in the general area is used for agricultural, domestic, or industrial purposes. Domestic water within the area is supplied by Cal Water ' A well survey, performed by Western Geologic Resources, Inc , in 1990, using California Department of Water Resources (DWR) well logs, identified ten registered wells and potentially three other wells within a one-half mile ' radius of the protect site Figure 7 and Table 4 in Attachment D provide estimated locations of the wells as well as known information regarding owner and address One domestic well and ten industrial wells are located north of the site One domestic well is located south of the site and one industrial well is located west of the site All these wells are either upgradient or cross-gradient from the underground tanks ' A well not identified by Western Geologic Resources' survey was Well Station 72 installed and operated by Cal Water Services Inc This well is located approximately 1/4 mile east of the site (downgradient from the tank site) This domestic well was last operated in 1978 According to Cal Water, most wells on the west side of Stockton, including well 72, are not operational